The DAX, or Deutscher Aktienindex, is a stock market index that measures the performance of the 30 largest and most actively traded blue-chip companies listed on the Frankfurt Stock Exchange in Germany. The index was first introduced on July 1, 1988, and has since become one of Europe's most important and widely recognized stock indices.

The DAX was created by the Deutsche Boerse Group, which is the largest German stock exchange and one of the most important exchanges in the world. The index was designed as a benchmark for the performance of the German stock market and continues to be used as an important barometer of the country's economic health.

The companies listed on the DAX are some of Germany's most important and prominent firms, including multinational corporations such as BMW, Siemens, and Deutsche Bank. These firms are leaders in their respective industries and are seen as key drivers of the German economy.

The DAX's importance grew significantly in the 1990s, as Germany emerged as the economic powerhouse of Europe. As German companies continued to expand their operations overseas, the DAX became an increasingly important benchmark for global investors looking to measure the performance of German firms.

Today, the DAX is one of the most widely used benchmarks for the European stock market and is closely followed by financial analysts and investors around the world. The strength and stability of the index are seen as critical to the health of the European economy as a whole.